1. Field of the Invention
The present invention relates to a clamp mechanism and a lower blade supporting mechanism for a travelling cutting machine which, while travelling along a continuously produced steel pipe, clamps the steel pipe when the travelling speed of the machine coincides with that of the steel pipe, and while lowering an upper blade, cuts the steel pipe between the upper blade and a lower blade provided at the clamp mechanism.
2. Background of the Art
Conventionally, a clamp mechanism for a travelling cutting machine is disclosed and well-known in the U.S. Pat. No. 4,637,287 and U.S. Pat. No. 5,161,444.
The clamp mechanism on the above prior art is constructed as shown in FIG. 12, in which a pneumatic cylinder 50 vertically moves a wedge piston 51 so that a wedge 52 disposed at the lower end of the wedge piston 51 is alternately driven into or pulled out from between the lower-right-blade holder 22 and a lower-left blade-holder 23 and a clamp is laterally divided into two at the lower-right-blade holder 22 and lower-left blade-holder 23.
The lower-right-blade holder 22 is integral with a right lower blade 2, and the lower-left blade-holder 23 is integral with a left lower blade 3, the right lower blade 2 and left lower blade 3 constituting the clamp mechanism.
In detail, when the wedge piston 51 of the pneumatic cylinder 50 depresses the wedge 52, tapered cams 24 and 25 at the lower-right-blade holder 22 and lower-left blade-holder 23 are expanded therebetween so that the clamp mechanism formed by the left lower blade 3 and right lower blade 2 closes in a perpendicular direction to a steel pipe 1. Conversely, when the wedge piston 51 of the pneumatic cylinder 50 rises to pull out the wedge 52, an open-biasing spring 13 operates to move the lower-right-blade holder 22 and lower-left blade-holder 23 in an open position.
Conventionally, the wedge piston 51 of the pneumatic cylinder 50 moves vertically by switching a solenoid valve 53, the right lower blade 2 and left lower blade 3 being semicircular and operating also as the clamp mechanism.
The timing of the clamp opening and closing to cut the steel pipe is such that it does not disturb the following operations.
1. A die set mechanism move from a home position in the travelling direction of the pipe.
2. When the travelling speed of the die set mechanism coincides with the moving speed of the pipe, a signal is given to the solenoid coil so as to start the pipe clamping operation.
3. Upon completion of the pipe clamping operation, a cut command is given to lower a vertically movable base having an upper blade and a top cut blade.
4. Upon completion of the pipe cut operation, a command is given to the solenoid coil to release the pipe clamping.
5. Upon released the pipe, a command is given to the solenoid coil to reversely move the die set to return it to the home position.
In the above-mentioned pipe clamping mechanism, the timing of switching mechanisms in the valve once the electric signal has been given in the solenoid coil and that of exchanging the pipe and of flowing compressed air in the pneumatic cylinder to operate the piston thereof are problematic.
The total cycle time varies due to variation in the operation time of the mechanisms due to factors such as air temperature and lubrication conditions which create frictional resistance. Reduction of total cycle time for high speed cutting is problematic in that variation in operation time of the clamping mechanism, for example, can cause the upper blade to start cutting while the pipe is yet unclamped, resulting in damage to the upper blade. The travelling die set mechanism must be connected by an air pipe to a fixed air pressure supply, which complicates the mechanism.
In the prior art, a lower blade support mechanism is constructed as shown in FIGS. 10 and 11.
In detail, the lower blade mechanism is divided into four parts: a lower left front blade 3f, a lower left rear blade 3r, a lower right front right blade 2f and a lower right rear blade 2r. Among the four parts, the lower right front blade 2f and lower right rear blade 2r are connected to a lower-right blade-holder 22 with connecting bolts 41 and the lower left front blade 3f and lower left rear blade 3r are connected to the lower-left blade-holder 33 with said connecting bolts 41. Thus, two components comprising said four blades are disposed sandwiching therebetween an upper blade 9, all perpendicular to the steel pipe 1, said components being are bilaterally symmetrically disposed.
The lower blades are in four parts, disposed bilaterally in two double-bladed components because they are also used as the clamp mechanism for the steel pipe 1, thus must independently move to the right and left to expand or close a gap therebetween when clamping and releasing, and because the thickness of the sandwiched blade 9 must correspond to the thickness of a pipe to be cut, whereby the gap through which the upper blade 9 is passable can be changed.
The lower blades are connected to the lower blade holders in a conventional method as shown in FIGS. 10 and 11.
Adjusting shims 40 for adjusting the gap t through which the upper blade 9 passes are sandwiched between the lower blades which are longitudinally positioned corresponding to the thickness of the upper blade 9.
A disadvantage of the conventional lower blade supporting mechanism is that in order to change the thickness of the upper blade, the four connecting bolts must be removed from the lower blades on the die set, and the four adjusting shims 40 separately interposed between the blade and the blade holders must be replaced with other shims, necessitating a difficult physical posture for an operator, constituting bending himself forward onto the die set frame 29.
Moreover, changing size of the steel pipe 1 or the thickness of the upper blade 9 takes much time. Further, cutting surfaces c through which the upper blade 9 passes and fixed surfaces d in contact with the lower-right blade-holder 22 and lower-left blade-holder 23 must be fine-ground in parallel, and the lower right blade 2 and the lower left blade 3 must be machined, and requiring much time.